[meteorite-list] Sensor on Mars Rover to Measure Radiation Environment (MSL)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 9 Nov 2010 12:14:34 -0800 (PST)
Message-ID: <201011092014.oA9KEYD1007976_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2010-376

Sensor on Mars Rover to Measure Radiation Environment
Jet Propulsion Laboratory
November 09, 2010

About eight months before the NASA rover Curiosity touches down on Mars
in August 2012, the mission's science measurements will begin much
closer to Earth.

The Mars Science Laboratory mission's Radiation Assessment Detector, or
RAD, will monitor naturally occurring radiation that can be unhealthful
if absorbed by living organisms. It will do so on the surface of Mars,
where there has never before been such an instrument, as well as during
the trip between Mars and Earth.

RAD's measurements on Mars will help fulfill the mission's key goals of
assessing whether Curiosity's landing region on Mars has had conditions
favorable for life and for preserving evidence about life. This
instrument also will do an additional job. Unlike any of the nine others
in this robotic mission's science payload, RAD has a special task and
funding from the part of NASA that is planning human exploration beyond
Earth orbit. It will aid design of human missions by reducing
uncertainty about how much shielding from radiation future astronauts
will need. The measurements between Earth and Mars, as well as the
measurements on Mars, will serve that purpose.

"No one has fully characterized the radiation environment on the surface
of another planet. If we want to send humans there, we need to do that,"
said RAD Principal Investigator Don Hassler of the Boulder, Colo.,
branch of the Southwest Research Institute.

Whether the first destination for human exploration beyond the moon is
an asteroid or Mars, the travelers will need protection from the
radiation environment in interplanetary space. Hassler said, "The
measurements we get during the cruise from Earth to Mars will help map
the distribution of radiation throughout the solar system and be useful
in mission design for wherever we send astronauts."

RAD will monitor high-energy atomic and subatomic particles coming from
the sun, from distant supernovas and from other sources. These particles
constitute the radiation that could be harmful to any microbes near the
surface of Mars or to astronauts on a Mars mission. Galactic cosmic
rays, coming from supernova explosions and other events extremely far
from our own solar system, are a variable shower of charged particles.
In addition, the sun itself spews electrons, protons and heavier ions in
"solar particle events" fed by solar flares and ejections of matter from
the sun's corona. Astronauts might need to move into havens with extra
shielding on an interplanetary spacecraft or on Mars during solar
particle events.

Earth's magnetic field and atmosphere provide effective shielding for
our home planet against the possible deadly effects of galactic cosmic
rays and solar particle events. Mars, though, lacks a global magnetic
field and has only about one percent as much atmosphere as Earth. Just
to find high-enough radiation levels on Earth for checking and
calibrating RAD, the instrument team needed to put it inside major
particle-accelerator research facilities in the United States, Europe,
Japan and South Africa.

An instrument on NASA's Mars Odyssey orbiter, which reached Mars in
2001, assessed radiation levels above the Martian atmosphere. Current
estimates of the radiation environment at the planet's surface rely on
modeling of how the thin atmosphere affects the energetic particles, but
uncertainty in the modeling remains large. "A single energetic particle
hitting the top of the atmosphere can break up into many particles -- a
cascade of lower-energy particles that might be more damaging to life
than a single high-energy particle," Hassler noted.

The 1.7-kilogram (3.8-pound) RAD instrument has an upward-pointing,
wide-angle telescope with detectors for charged particles with masses up
to that of iron. It can also detect secondary neutrons coming from both
the Mars atmosphere above and Mars surface material below. Hassler's
international RAD team includes experts in instrument design, astronaut
safety, atmospheric science, geology and other fields.

Southwest Research Institute, in Boulder and in San Antonio, Texas, and
Christian Albrechts University, in Kiel, Germany, built RAD with funding
from the NASA Exploration Systems Mission Directorate and Germany's
national aerospace research center: Deutschen Zentrum f??r Luft- und
Raumfahrt. The team assembling and testing the Mars Science Laboratory
spacecraft at NASA's Jet Propulsion Laboratory in Pasadena, Calif.,
installed RAD onto Curiosity last month for the late-2011 launch.

RAD measurements during the trip from Earth to Mars will enable
correlations with instruments on other spacecraft that monitor solar
particle events and galactic cosmic rays in Earth's neighborhood, then
will yield data about the radiation environment farther from Earth.

Once on Mars, the rover's prime mission will last a full Martian year --
nearly two Earth years. A one-time set of measurements by RAD would not
suffice for determining the radiation environment on the surface,
because radiation levels vary on time frames both longer than a year and
shorter than an hour. Operational planning for Curiosity anticipates
that RAD will record measurements for 15 minutes of every hour
throughout the prime mission.

Radiation levels probably make the surface of modern Mars inhospitable
for microbial life. The measurements from RAD will feed calculations of
how deeply a possible future robot on a life-detection mission might
need to dig or drill to reach a microbial safe zone. For assessing
whether the surface radiation environment could have been hospitable for
microbes in Mars' distant past, researchers will combine RAD's
measurements with estimates of how the activity of the sun and the
atmosphere of Mars have changed in the past few billion years.

"The primary science goal of Curiosity is to determine whether its
landing site is, or ever was, a habitable environment, a place friendly
to life," said JPL's Ashwin Vasavada, deputy project scientist for the
Mars Science Laboratory. "That involves looking both for conditions that
would support life as well as for those that would be hazardous to life
or its chemical predecessors. Natural, high-energy radiation is just
such a hazard, and RAD will give us the first look at the present level
of this radiation and help us to better estimate radiation levels
throughout Mars' history."

JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Science Laboratory Project for NASA's Science Mission
Directorate, Washington. For more information about the mission, see
http://mars.jpl.nasa.gov/msl/.

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov

2010-376
Received on Tue 09 Nov 2010 03:14:34 PM PST